Historical contingency is an important idea in biology and evolution. It is the theory that the paths that life can evolve on are constrained by historical events that are often random. This was perhaps most succinctly described by Stephen Jay Gould, when he proposed the thought experiment of rewinding the tape of evolution backwards and replaying it. The question is: "would life evolve in the same way or in some very different manner?" This idea cuts to the heart of many issues surrounding the inevitability of humanity and determinism.